As a glass for a data storage medium substrate such as a magnetic disk or an optical disk, for example, a lithium-containing aluminosilicate glass with a high Young's modulus or a glass obtained by conducting a chemical strengthening treatment thereon (for example, see PTL 1), or a crystallized glass in which a glass having a specific composition is heat-treated to precipitate a crystal layer (for example, see PTL 2) is used.
In recent years, in accordance with increase in a storage capacity of a hard disk drive, densification of recording progresses at a quick pace. However, along with the densification of recording, miniaturization of a magnetic particle impairs thermal stability, and a crosstalk or a decreased SN ratio of a regenerative signal becomes a problem. Therefore, as a fusion technology of light and magnetism, a technology of thermally assisted magnetic recording attracts attention.
The technology of thermally assisted magnetic recording is a technology of recording by applying an external magnetic field in a state where a magnetic recording layer is irradiated with laser light or near field light to locally heat a portion and coercive force of the portion is lowered, and reading the recorded magnetization with a GMR element or the like. According to the technology of thermally assisted magnetic recording, since recording to a medium having high coercive force can be performed, it is possible to miniaturize a magnetic particle while maintaining thermal stability.